今天看Thinking in C++ 2nd v2第一章的关于set_unexpected, 测试书里的代码, 发现和书上的结果不同, 代码如下:
//: C01:BadException.cpp {-bor}
#include <exception> // For std::bad_exception
#include <iostream>
#include <cstdio>
using namespace std;
// Exception classes:
class A {};
class B {};
// terminate() handler
void my_thandler() {
cout << "terminate called" << endl;
exit(0);
}
// unexpected() handlers
void my_uhandler1() { throw A(); }
void my_uhandler2() { throw; }
// If we embed this throw statement in f or g,
// the compiler detects the violation and reports
// an error, so we put it in its own function.
void t() { throw B(); }
void f() throw(A) { t(); }
void g() throw(A, bad_exception) { t(); }
int main() {
set_terminate(my_thandler);
set_unexpected(my_uhandler1);
try {
f();
} catch(A&) {
cout << "caught an A from f" << endl;
}
set_unexpected(my_uhandler2);
try {
g();
} catch(bad_exception&) {
cout << "caught a bad_exception from g" << endl;
}
try {
f();
} catch(...) {
cout << "This will never print" << endl;
}
} ///:~
书上说结果将会调用自定义的异常handler:
caught an A from f
caught a bad_exception from g
terminate called
可我用Visual C++运行的结果是:
terminate called
立刻跑到Google搜索, 结果搜到MSDN关于set_unexpected的页面:
MSDN最后说:
In the current Microsoft implementation of C++ exception handling, unexpected calls terminate by default and is never called by the exception-handling run-time library. There is no particular advantage to calling unexpected rather than terminate.
噢, 微软就是牛哈, 说不支持就是不支持~ 不过感觉微软做的也对, 这些东东用多了代码就会变的很乱了. 像这种问题还是应该使用良好的设计来避免~
